Thorchain (https://thorchain.org/) is one of them but i assume a decent work would be reuired to upgrade nodes/decentralized custody on hive side, and then getting them help us integerate.
As hive might not bring them a lot of volume, so our case for them could be week, but if DAO provides intial liquity and promotion etc. they may take it.
Thorswap is one of app on thorchain: https://app.thorswap.finance/swap
That's why we are building @vsc.network to not only help solve the custody problem but also bring smart contracts to HIVE that allows any chain to easily integrate with HIVE via a smart contract. We can already do cross chain swaps using HTLC, with full Bitcoin to HIVE wrapping under heavy development. It's only a matter of time.